An engine as mounted in a vehicle is cooled by air or water to maintain an appropriate operation temperature. In the water-cooling method, the engine is cooled by circulating a coolant using a water pump and a thermostat between the water jacket of the engine and the radiator.
FIG. 7 shows a conventional vehicle engine coolant pipeline using the water-cooling method. In FIG. 7, 102 is a vehicle engine, and 104 is a water jacket associated with the engine. The engine 102 includes a radiator 106 for cooling the hot coolant received from the water jacket 104; a water pump 108 for circulating the coolant at a high pressure; a thermostat 110 for admitting or stopping the circulation of the coolant to the radiator 106 depending on the temperature of the coolant; and a heater core 112 for heating a passenger compartment (not shown in FIG. 7) of the vehicle.
The radiator 106 and thermostat 110 are connected to each other through a radiator inlet hose 114 and a radiator outlet hose 116. The water pump 108 and the thermostat 110 are connected to each other through a water pipe 118. A heater inlet hose 120 connects the thermostat 110 and the heater core 112 to each other. A heater outlet hose 122 connects core 112 and the water pipe 118 to each other.
When the temperature of the coolant is equal to or lower than a preset temperature, the thermostat 110 closes and stops the circulation of the coolant in the radiator 106. The coolant flows from the water jacket 104 to the heater inlet hose 120, the heater core 112, and the heater outlet hose 122, and then through the water pipe 118 to the water pump 108 and back into the water jacket 104. On the other hand, when the coolant temperature is higher than the preset temperature, the thermostat 110 opens to admit the circulation of the coolant into the radiator 106. The coolant flows from the water jacket 104 to the radiator inlet hose 114, the radiator 106, the radiator outlet hose 116, the water pipe 118, the water pump 108 and back into the water jacket 104. At the same time, the coolant also circulates through the heater core 112 as described above.
FIG. 8 shows another conventional vehicle engine coolant pipeline, wherein 202 is a vehicle engine, 204 is a water jacket. The vehicle engine 202 includes a radiator 206 for cooling the coolant of the water jacket 204; a water pump 208 for circulating the coolant at a high pressure; a thermostat 210 for admitting or stopping the circulation of the coolant to the radiator 206 depending on the temperature of the coolant; and a heater core 212 for heating a passenger compartment (not shown in FIG. 8) of the vehicle.
A radiator inlet hose 214 connects the radiator 206 and thermostat 210 to each other. A radiator outlet hose 216, a water pipe 217, and a water hose 218 connect the radiator 206 and the water pump 208 to each other. The water hose 218 is connected to the water pump 208. A heater inlet hose 220 connects the thermostat 210 and a heater core 212 to each other. A heater outlet hose 222 connects the heater core 212 and the water pipe 217 to each other.
When the temperature of the coolant is equal to or lower than a preset temperature, the thermostat 210 closes and stops the circulation of the coolant to the radiator 206. Then the coolant flows from the water jacket 204 to the heater inlet hose 220, the heater core 212, the heater outlet hose 222, the water pipe 217, and the water hose 218 to the water pump 208 and back into the water jacket 204. On the other hand, when the temperature of the coolant is higher than the preset temperature, the thermostat 210 opens to admit the circulation of the coolant to the radiator 206. Then the coolant flows from the water jacket 204 to the radiator inlet hose 214, the radiator 206, the radiator outlet hose 216, the water pipe 217, the water hose 218, the water pump 208, and back into the water jacket 204. At the same time, the coolant also circulates through the heater core 212 as described above.
In the arrangement of FIG. 7, since the water pipe 118 connecting the water pump 108 to the thermostat 110 is provided under an exhaust manifold 124 of the engine, the exhaust heat heats the coolant pipeline. This may cause a problem when the vehicle engine is operating in a warm or heated condition. Furthermore, since the thermostat 110 is connected to the radiator inlet hose 114, the radiator outlet hose 116, and the water pipe 118 in the coolant pipeline shown in FIG. 7, the structure of a thermo-case 126 is complicated.
As to the arrangement of FIG. 8, since the radiator 206 is connected to the water pump 208 through the radiator outlet hose 216, water pipe 217, and water hose 218, the coolant pipeline is a long pipe of several parts. Furthermore, since the coolant pipeline shown in FIG. 8 normally has the water pipe 217 fixed to the vehicle transmission (not shown in FIG. 8), and since different types of transmissions are connected to the engine 202, this may require using different shapes of water pipes, thereby increasing the cost of the cooling system.